1. Field of the Invention
The present invention relates to a sheet processing device capable of folding a large-size sheet into a small-size folded sheet and punching the folded sheet, and an image forming apparatus including the sheet processing device.
2. Description of the Related Art
When a copy of a large-sized original document such as a drawing is made by a copier, the document is copied onto a large-sized sheet such as an A0-size sheet or an A1-size sheet in most cases. The large-sized sheet is usually folded into a small size to store the sheet in a convenient manner for saving storage space. However, if the sheet is manually folded, it takes a considerable time to fold the sheet. In some cases, it may take a longer time to fold the sheet manually than that to make a copy. Therefore, a sheet folding device capable of folding, for example, the A0-size sheet into an A4 size, is provided on a sheet discharging path of the copier.
In general, such a sheet folding device is mounted on an image forming apparatus such as a copier or a facsimile machine, and arranged in the downstream side of a sheet conveying direction. The sheet folding device includes a folding mechanism for folding a sheet with a predetermined method. The folding mechanism includes, for example, a punching unit that punches a hole in the folded sheet to bind the folded sheet.
A typical sheet folding device is disclosed in Japanese Patent No. 3173095. In the sheet folding device, a fold-data storing unit stores therein fold data. A folding unit folds a sheet based on the fold data stored in the fold-data storing unit. A sheet-running state detecting unit detects a running state of the sheet in the folding unit. A correction-data calculating unit obtains correction data based on a result of detection by the sheet-running state detecting unit. A fold-data correcting unit corrects the fold data stored in the fold-data storing unit based on the correction data obtained by the correction-data calculating unit. A fold-data updating unit updates the fold data stored in the fold-data storing unit.
However, a conventional sheet folding device including the one disclosed in Japanese Patent No. 3173095 requires a relatively large space for installing the sheet folding device because the sheet folding device is bulky due to including a folding mechanism that includes a punching unit. In addition, it is necessary to ensure extra space for a maintenance work, for example, for fixing a paper jam.